Fallback delegates for modification of an index structure

ABSTRACT

A method includes determining that a primary delegate device is unavailable. The method continues by identifying a fallback delegate device for changing a node of a hierarchical index structure using a deterministic function. The deterministic function includes performing a first modification of global namespace address of the unavailable primary delegate device to produce a first modified address identifier. The deterministic function further includes determining whether another delegate device of the plurality of delegate devices has a global namespace address corresponding to the first modified address identifier. When the global namespace address of other delegate device corresponds to the first modified address identifier, the method further includes processing a change to a node of the one or more nodes via the other delegate device as the fallback delegate device.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present U.S. Utility Patent Application claims priority pursuant to35 U.S.C. §119(e) to U.S. Provisional Application No. 62/248,636,entitled “SECURELY STORING DATA IN A DISPERSED STORAGE NETWORK”, filedOct. 30, 2015, which is hereby incorporated herein by reference in itsentirety and made part of the present U.S. Utility Patent Applicationfor all purposes.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

Not applicable.

INCORPORATION-BY-REFERENCE OF MATERIAL SUBMITTED ON A COMPACT DISC

Not applicable.

BACKGROUND OF THE INVENTION

Technical Field of the Invention

This invention relates generally to computer networks and moreparticularly to dispersing error encoded data.

Description of Related Art

Computing devices are known to communicate data, process data, and/orstore data. Such computing devices range from wireless smart phones,laptops, tablets, personal computers (PC), work stations, and video gamedevices, to data centers that support millions of web searches, stocktrades, or on-line purchases every day. In general, a computing deviceincludes a central processing unit (CPU), a memory system, userinput/output interfaces, peripheral device interfaces, and aninterconnecting bus structure.

As is further known, a computer may effectively extend its CPU by using“cloud computing” to perform one or more computing functions (e.g., aservice, an application, an algorithm, an arithmetic logic function,etc.) on behalf of the computer. Further, for large services,applications, and/or functions, cloud computing may be performed bymultiple cloud computing resources in a distributed manner to improvethe response time for completion of the service, application, and/orfunction. For example, Hadoop is an open source software framework thatsupports distributed applications enabling application execution bythousands of computers.

In addition to cloud computing, a computer may use “cloud storage” aspart of its memory system. As is known, cloud storage enables a user,via its computer, to store files, applications, etc. on an Internetstorage system. The Internet storage system may include a RAID(redundant array of independent disks) system and/or a dispersed storagesystem that uses an error correction scheme to encode data for storage.

In cloud storage systems, it is common to use one or more indexstructures to improve the ease of finding data. For example, one indexstructure is used for find data based on alphabetic indexing. As anotherexample, another index structure is used to find data based on key wordscontained in the title of the data. As yet another example, anotherindex structure is used to find data based on the type of data (e.g.,video, audio, text, pictures, etc.). As the data changes within thecloud storage system, one or more index structures may need to beupdated.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING(S)

FIG. 1 is a schematic block diagram of an embodiment of a dispersed ordistributed storage network (DSN) in accordance with the presentinvention;

FIG. 2 is a schematic block diagram of an embodiment of a computing corein accordance with the present invention;

FIG. 3 is a schematic block diagram of an example of dispersed storageerror encoding of data in accordance with the present invention;

FIG. 4 is a schematic block diagram of a generic example of an errorencoding function in accordance with the present invention;

FIG. 5 is a schematic block diagram of a specific example of an errorencoding function in accordance with the present invention;

FIG. 6 is a schematic block diagram of an example of a slice name of anencoded data slice (EDS) in accordance with the present invention;

FIG. 7 is a schematic block diagram of an example of dispersed storageerror decoding of data in accordance with the present invention;

FIG. 8 is a schematic block diagram of a generic example of an errordecoding function in accordance with the present invention;

FIG. 9 is a schematic block diagram of an embodiment of a hierarchicalindex structure in accordance with the present invention;

FIG. 10 is a schematic block diagram of an example of an index node inaccordance with the present invention;

FIG. 11 is a schematic block diagram of an example of a leaf node inaccordance with the present invention;

FIG. 12 is a schematic block diagram of an embodiment of establishing afallback delegate for updating a hierarchical index structure of a DSNin accordance with the present invention;

FIG. 13 is a logic diagram of an example of a method of establishing afallback delegate for a hierarchical index structure of a DSN inaccordance with the present invention;

FIG. 14 is a logic diagram of another example of a method ofestablishing a fallback delegate for a hierarchical index structure of aDSN in accordance with the present invention;

FIG. 15 is a schematic block diagram of an example of a global namespaceand geographic location with a DSN in accordance with the presentinvention; and

FIG. 16 is a diagram of an example of establishing a fallback delegatefor a hierarchical index structure of a DSN in accordance with thepresent invention.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 is a schematic block diagram of an embodiment of a dispersed, ordistributed, storage network (DSN) 10 that includes a plurality ofcomputing devices 12-16, a managing unit 18, an integrity processingunit 20, and a DSN memory 22. The components of the DSN 10 are coupledto a network 24, which may include one or more wireless and/or wirelined communication systems; one or more non-public intranet systemsand/or public internet systems; and/or one or more local area networks(LAN) and/or wide area networks (WAN).

The DSN memory 22 includes a plurality of storage units 36 that may belocated at geographically different sites (e.g., one in Chicago, one inMilwaukee, etc.), at a common site, or a combination thereof. Forexample, if the DSN memory 22 includes eight storage units 36, eachstorage unit is located at a different site. As another example, if theDSN memory 22 includes eight storage units 36, all eight storage unitsare located at the same site. As yet another example, if the DSN memory22 includes eight storage units 36, a first pair of storage units are ata first common site, a second pair of storage units are at a secondcommon site, a third pair of storage units are at a third common site,and a fourth pair of storage units are at a fourth common site. Notethat a DSN memory 22 may include more or less than eight storage units36. Further note that each storage unit 36 includes a computing core (asshown in FIG. 2, or components thereof) and a plurality of memorydevices for storing dispersed error encoded data.

Each of the computing devices 12-16, the managing unit 18, and theintegrity processing unit 20 include a computing core 26, which includesnetwork interfaces 30-33. Computing devices 12-16 may each be a portablecomputing device and/or a fixed computing device. A portable computingdevice may be a social networking device, a gaming device, a cell phone,a smart phone, a digital assistant, a digital music player, a digitalvideo player, a laptop computer, a handheld computer, a tablet, a videogame controller, and/or any other portable device that includes acomputing core. A fixed computing device may be a computer (PC), acomputer server, a cable set-top box, a satellite receiver, a televisionset, a printer, a fax machine, home entertainment equipment, a videogame console, and/or any type of home or office computing equipment.Note that each of the managing unit 18 and the integrity processing unit20 may be separate computing devices, may be a common computing device,and/or may be integrated into one or more of the computing devices 12-16and/or into one or more of the storage units 36.

Each interface 30, 32, and 33 includes software and hardware to supportone or more communication links via the network 24 indirectly and/ordirectly. For example, interface 30 supports a communication link (e.g.,wired, wireless, direct, via a LAN, via the network 24, etc.) betweencomputing devices 14 and 16. As another example, interface 32 supportscommunication links (e.g., a wired connection, a wireless connection, aLAN connection, and/or any other type of connection to/from the network24) between computing devices 12 and 16 and the DSN memory 22. As yetanother example, interface 33 supports a communication link for each ofthe managing unit 18 and the integrity processing unit 20 to the network24.

Computing devices 12 and 16 include a dispersed storage (DS) clientmodule 34, which enables the computing device to dispersed storage errorencode and decode data (e.g., data 40) as subsequently described withreference to one or more of FIGS. 3-8. In this example embodiment,computing device 16 functions as a dispersed storage processing agentfor computing device 14. In this role, computing device 16 dispersedstorage error encodes and decodes data on behalf of computing device 14.With the use of dispersed storage error encoding and decoding, the DSN10 is tolerant of a significant number of storage unit failures (thenumber of failures is based on parameters of the dispersed storage errorencoding function) without loss of data and without the need for aredundant or backup copies of the data. Further, the DSN 10 stores datafor an indefinite period of time without data loss and in a securemanner (e.g., the system is very resistant to unauthorized attempts ataccessing the data).

In operation, the managing unit 18 performs DS management services. Forexample, the managing unit 18 establishes distributed data storageparameters (e.g., vault creation, distributed storage parameters,security parameters, billing information, user profile information,etc.) for computing devices 12-14 individually or as part of a group ofuser devices. As a specific example, the managing unit 18 coordinatescreation of a vault (e.g., a virtual memory block associated with aportion of an overall namespace of the DSN) within the DSN memory 22 fora user device, a group of devices, or for public access and establishesper vault dispersed storage (DS) error encoding parameters for a vault.The managing unit 18 facilitates storage of DS error encoding parametersfor each vault by updating registry information of the DSN 10, where theregistry information may be stored in the DSN memory 22, a computingdevice 12-16, the managing unit 18, and/or the integrity processing unit20.

The managing unit 18 creates and stores user profile information (e.g.,an access control list (ACL)) in local memory and/or within memory ofthe DSN memory 22. The user profile information includes authenticationinformation, permissions, and/or the security parameters. The securityparameters may include encryption/decryption scheme, one or moreencryption keys, key generation scheme, and/or data encoding/decodingscheme.

The managing unit 18 creates billing information for a particular user,a user group, a vault access, public vault access, etc. For instance,the managing unit 18 tracks the number of times a user accesses anon-public vault and/or public vaults, which can be used to generate aper-access billing information. In another instance, the managing unit18 tracks the amount of data stored and/or retrieved by a user deviceand/or a user group, which can be used to generate a per-data-amountbilling information.

As another example, the managing unit 18 performs network operations,network administration, and/or network maintenance. Network operationsincludes authenticating user data allocation requests (e.g., read and/orwrite requests), managing creation of vaults, establishingauthentication credentials for user devices, adding/deleting components(e.g., user devices, storage units, and/or computing devices with a DSclient module 34) to/from the DSN 10, and/or establishing authenticationcredentials for the storage units 36. Network administration includesmonitoring devices and/or units for failures, maintaining vaultinformation, determining device and/or unit activation status,determining device and/or unit loading, and/or determining any othersystem level operation that affects the performance level of the DSN 10.Network maintenance includes facilitating replacing, upgrading,repairing, and/or expanding a device and/or unit of the DSN 10.

The integrity processing unit 20 performs rebuilding of ‘bad’ or missingencoded data slices. At a high level, the integrity processing unit 20performs rebuilding by periodically attempting to retrieve/list encodeddata slices, and/or slice names of the encoded data slices, from the DSNmemory 22. For retrieved encoded slices, they are checked for errors dueto data corruption, outdated version, etc. If a slice includes an error,it is flagged as a ‘bad’ slice. For encoded data slices that were notreceived and/or not listed, they are flagged as missing slices. Badand/or missing slices are subsequently rebuilt using other retrievedencoded data slices that are deemed to be good slices to produce rebuiltslices. The rebuilt slices are stored in the DSN memory 22.

FIG. 2 is a schematic block diagram of an embodiment of a computing core26 that includes a processing module 50, a memory controller 52, mainmemory 54, a video graphics processing unit 55, an input/output (IO)controller 56, a peripheral component interconnect (PCI) interface 58,an IO interface module 60, at least one IO device interface module 62, aread only memory (ROM) basic input output system (BIOS) 64, and one ormore memory interface modules. The one or more memory interfacemodule(s) includes one or more of a universal serial bus (USB) interfacemodule 66, a host bus adapter (HBA) interface module 68, a networkinterface module 70, a flash interface module 72, a hard drive interfacemodule 74, and a DSN interface module 76.

The DSN interface module 76 functions to mimic a conventional operatingsystem (OS) file system interface (e.g., network file system (NFS),flash file system (FFS), disk file system (DFS), file transfer protocol(FTP), web-based distributed authoring and versioning (WebDAV), etc.)and/or a block memory interface (e.g., small computer system interface(SCSI), internet small computer system interface (iSCSI), etc.). The DSNinterface module 76 and/or the network interface module 70 may functionas one or more of the interface 30-33 of FIG. 1. Note that the IO deviceinterface module 62 and/or the memory interface modules 66-76 may becollectively or individually referred to as IO ports.

FIG. 3 is a schematic block diagram of an example of dispersed storageerror encoding of data. When a computing device 12 or 16 has data tostore it disperse storage error encodes the data in accordance with adispersed storage error encoding process based on dispersed storageerror encoding parameters. The dispersed storage error encodingparameters include an encoding function (e.g., information dispersalalgorithm, Reed-Solomon, Cauchy Reed-Solomon, systematic encoding,non-systematic encoding, on-line codes, etc.), a data segmentingprotocol (e.g., data segment size, fixed, variable, etc.), and per datasegment encoding values. The per data segment encoding values include atotal, or pillar width, number (T) of encoded data slices per encodingof a data segment (i.e., in a set of encoded data slices); a decodethreshold number (D) of encoded data slices of a set of encoded dataslices that are needed to recover the data segment; a read thresholdnumber (R) of encoded data slices to indicate a number of encoded dataslices per set to be read from storage for decoding of the data segment;and/or a write threshold number (W) to indicate a number of encoded dataslices per set that must be accurately stored before the encoded datasegment is deemed to have been properly stored. The dispersed storageerror encoding parameters may further include slicing information (e.g.,the number of encoded data slices that will be created for each datasegment) and/or slice security information (e.g., per encoded data sliceencryption, compression, integrity checksum, etc.).

In the present example, Cauchy Reed-Solomon has been selected as theencoding function (a generic example is shown in FIG. 4 and a specificexample is shown in FIG. 5); the data segmenting protocol is to dividethe data object into fixed sized data segments; and the per data segmentencoding values include: a pillar width of 5, a decode threshold of 3, aread threshold of 4, and a write threshold of 4. In accordance with thedata segmenting protocol, the computing device 12 or 16 divides the data(e.g., a file (e.g., text, video, audio, etc.), a data object, or otherdata arrangement) into a plurality of fixed sized data segments (e.g., 1through Y of a fixed size in range of Kilo-bytes to Tera-bytes or more).The number of data segments created is dependent of the size of the dataand the data segmenting protocol.

The computing device 12 or 16 then disperse storage error encodes a datasegment using the selected encoding function (e.g., Cauchy Reed-Solomon)to produce a set of encoded data slices. FIG. 4 illustrates a genericCauchy Reed-Solomon encoding function, which includes an encoding matrix(EM), a data matrix (DM), and a coded matrix (CM). The size of theencoding matrix (EM) is dependent on the pillar width number (T) and thedecode threshold number (D) of selected per data segment encodingvalues. To produce the data matrix (DM), the data segment is dividedinto a plurality of data blocks and the data blocks are arranged into Dnumber of rows with Z data blocks per row. Note that Z is a function ofthe number of data blocks created from the data segment and the decodethreshold number (D). The coded matrix is produced by matrix multiplyingthe data matrix by the encoding matrix.

FIG. 5 illustrates a specific example of Cauchy Reed-Solomon encodingwith a pillar number (T) of five and decode threshold number of three.In this example, a first data segment is divided into twelve data blocks(D1-D12). The coded matrix includes five rows of coded data blocks,where the first row of X11-X14 corresponds to a first encoded data slice(EDS 1_1), the second row of X21-X24 corresponds to a second encodeddata slice (EDS 2_1), the third row of X31-X34 corresponds to a thirdencoded data slice (EDS 3_1), the fourth row of X41-X44 corresponds to afourth encoded data slice (EDS 4_1), and the fifth row of X51-X54corresponds to a fifth encoded data slice (EDS 5_1). Note that thesecond number of the EDS designation corresponds to the data segmentnumber.

Returning to the discussion of FIG. 3, the computing device also createsa slice name (SN) for each encoded data slice (EDS) in the set ofencoded data slices. A typical format for a slice name 80 is shown inFIG. 6. As shown, the slice name (SN) 80 includes a pillar number of theencoded data slice (e.g., one of 1-T), a data segment number (e.g., oneof 1-Y), a vault identifier (ID), a data object identifier (ID), and mayfurther include revision level information of the encoded data slices.The slice name functions as, at least part of, a DSN address for theencoded data slice for storage and retrieval from the DSN memory 22.

As a result of encoding, the computing device 12 or 16 produces aplurality of sets of encoded data slices, which are provided with theirrespective slice names to the storage units for storage. As shown, thefirst set of encoded data slices includes EDS 1_1 through EDS 5_1 andthe first set of slice names includes SN 1_1 through SN 5_1 and the lastset of encoded data slices includes EDS 1_Y through EDS 5_Y and the lastset of slice names includes SN 1_Y through SN 5_Y.

FIG. 7 is a schematic block diagram of an example of dispersed storageerror decoding of a data object that was dispersed storage error encodedand stored in the example of FIG. 4. In this example, the computingdevice 12 or 16 retrieves from the storage units at least the decodethreshold number of encoded data slices per data segment. As a specificexample, the computing device retrieves a read threshold number ofencoded data slices.

To recover a data segment from a decode threshold number of encoded dataslices, the computing device uses a decoding function as shown in FIG.8. As shown, the decoding function is essentially an inverse of theencoding function of FIG. 4. The coded matrix includes a decodethreshold number of rows (e.g., three in this example) and the decodingmatrix in an inversion of the encoding matrix that includes thecorresponding rows of the coded matrix. For example, if the coded matrixincludes rows 1, 2, and 4, the encoding matrix is reduced to rows 1, 2,and 4, and then inverted to produce the decoding matrix.

FIG. 9 is a diagram illustrating an example of a distributed indexstructure 350 of one or more indexes utilized to access a data object ofone or more data objects 1_1 through 1_w, 3_1 through 3_w, 4_1 through4_w, etc., where at least some of the one or more data objects arestored in at least one of a distributed storage and task network (DSTN)and a dispersed storage network (DSN), and where a data object of theone or more data objects is dispersed storage error encoded to produce aplurality sets of encoded data slices, and where the plurality of setsof encoded data slices are stored in the DSN (e.g., and/or DSTN)utilizing a common source name (e.g., DSN address). The source nameprovides a DSTN and/or DSN address including one or more of vaultidentifier (ID) (e.g., such a vault ID associates a portion of storageresources of the DSN with one or more DSN user devices), a vaultgeneration indicator (e.g., identify a vault generation of one or moreof generations), and an object number that corresponds to the dataobject (e.g., a random number assigned to the data object when the dataobject is stored in the DSN).

The distributed index structure 350 includes at least two nodesrepresented in the index structure as nodes associated with two or morenode levels. One or more nodes of the at least two nodes of thedistributed index structure 350 may be dispersed storage error encodedto produce one or more sets of encoded index slices. The one or moresets of encoded index slices may be stored in at least one of a localmemory, a DSN memory, and a distributed storage and task network (DSTN)module. For example, each node of a 100 node distributed index structureare individually dispersed storage error encoded to produce at least 100sets of encoded index slices for storage in the DSTN module. As anotherexample, the 100 node index structure is aggregated into one index fileand the index file is dispersed storage error encoded to produce a setof encoded index slices for storage in the DSTN module.

Each node of the at least two nodes includes at least one of an indexnode and a leaf node. One index node of the at least two nodes includesa root index node. Alternatively, the distributed index structure 350includes just one node, wherein the one node is a leaf node and wherethe leaf node is a root node. The distributed index structure 350 mayinclude any number of index nodes, any number of leaf nodes, and anynumber of node levels. Each level of the any number of node levelsincludes nodes of a common node type. For example, all nodes of nodelevel 4 are leaf nodes and all nodes of node level 3 are index nodes. Asanother example, as illustrated, the distributed index structure 350includes eight index nodes and eight leaf nodes, where the eight indexnodes are organized in three node levels, where a first node levelincludes a root index node 1_1, a second node level includes index nodes2_1, 2_2, and 2_3, and a third node level includes index nodes 3_1, 3_2,3_3, 3_4, and 3_5, and where the eight leaf nodes are organized in alast (e.g., fourth) node level, where the last node level includes leafnodes 4_1, 4_2, 4_3, 4_4, 4_5, 4_6, 4_7, and 4_8.

Each data object of the one more data objects is associated with atleast one index key per distributed index structure of the one or moredistributed indexes, where the index key includes a searchable elementof the distributed index and may be utilized to locate the data objectin accordance with key type traits. An index key type of an index keyincludes a category of the index key (e.g. string integer, etc.). Anindex key type exhibits traits. Each index key is associated with one ormore key type traits (e.g., for an associated index structure), where akey type traits includes one or more of a type indicator, a traitindicator, a comparing function (e.g., defining how an associate indexkey of this type should be compared, such as sorting and/ormanipulation, to other such index keys), a serialization function (e.g.,encoding function for storage), a de-serialization function (e.g.,decoding function for retrieval), and an absolute minimum value of theindex key.

Each leaf node of the at least two nodes may be associated with one ormore data objects. The association includes at least one of, for eachdata object of the one more data objects, storing an index keyassociated with the data object in the leaf node, storing a source nameassociated with the data object in the leaf node, and storing the dataobject in the leaf node. For example, leaf node 4_2 includes a dataobject 4_2 and an index key associated with data object 4_2. As anotherexample, leaf node 4_3 includes source names associated with data object3_1 through 3_w and index keys associated with data object 3_1 through3_w. Each leaf node is associated with a minimum index key, where theminimum index key is a minimum value of one or more index keysassociated with the one or more data objects in accordance with the keytype traits (e.g., sorted utilizing a comparing function of the key typetraits to identify the minimum value).

Each leaf node is a child in a parent-child relationship with one indexnode, where the one index node is a parent in the parent-childrelationship. Each child node has one parent node and each parent nodehas one or more child nodes. The one index node (e.g., parent node)stores a minimum index key associated with the leaf node (e.g., childnode). As such, a parent node stores a minimum index key for each childnode of the one or more child nodes. Two index nodes may form aparent-child relationship. In such a parent-child relationship, aparent-child node pair is represented in the index structure with aparent node of the parent-child relationship associated with a parentnode level that is one level above in the index structure than a childnode level associated with a child node of the parent-childrelationship.

A leaf node is a sibling node of another leaf node when a minimum indexkey associated with the leaf node is ordered greater than a last minimumindex key associated with the other leaf node, where the last minimumindex key associated with the leaf node is sorted above any other lastminimum index keys associated with any other lower order leaf nodes andwhere the minimum index key associated with the leaf node is orderedless than any other minimum index keys associated with any other higherorder leaf nodes. A sibling node of a node is represented in the indexstructure on a common level with the node and one node position to theright. A last node on the far right of a node level has a no sibling(e.g., null sibling). All other nodes, if any, other than a last farright node, of a common node level have a sibling node. For example,leaf node 4_2 is a sibling node to leaf node 4_1, leaf node 4_3 is asibling node to leaf node 4_2, etc., leaf node 4_8 is a sibling node toleaf node 4_7 and leaf node 4_8 has no sibling node.

Each index node of the at least two nodes may be associated with one ormore child nodes. Such a child node includes at least one of anotherindex node or a leaf node. The association includes, for each child nodeof the one more child nodes, storing a minimum index key associated withthe child node in the index node and storing a source name associatedwith the child node in the index node. Each child node is associatedwith a minimum index key, where the minimum index key is a minimum valueof one or more index keys associated with the child node (e.g., theminimum index key is a minimum value of one or more index keysassociated with one or more children nodes of the child node or one ormore data objects of the child node in accordance with the key typetraits, sorted utilizing a comparing function of the key type traits toidentify the minimum value when the child node is a leaf node). Forexample, index node 3_2 includes a minimum index key (e.g., of dataobject 3_1) and source name associated with leaf node 4_3. As anotherexample, index node 3_3 includes a minimum index key and source nameassociated with leaf node 4_4 and another minimum index key and anothersource name associated with leaf node 4_5. As yet another example, indexnode 2_3 includes a minimum index key and source name associated withindex node 3_4 and minimum index key and another source name associatedwith index node 3_5.

An index node is a sibling node of another index node when a minimumindex key associated with the index node is ordered greater than a lastminimum index key associated with the other index node, where the lastminimum index key associated with the index node is sorted above anyother last minimum index keys associated with any other lower orderindex nodes and where the minimum index key associated with the indexnode is ordered less than any other minimum index keys associated withany other higher order index nodes. For example, index node 3_2 is asibling node to index node 3_1, index node 3_3 is a sibling node toindex node 3_2, etc., index node 3_6 is a sibling node to index node 3_5and index node 3_6 has no sibling node.

FIG. 10 is a diagram illustrating an example of an index node structure352 for an index node that includes index node information 356, siblingnode information 358, and children node information 360. Alternatively,there is no sibling node information 358 when the index node has nosibling node. The index node information 356 includes one or more of anindex node source name field 362, an index node revision field 364, anda node type field 366. Inclusion and/or use of the index node sourcename field 362 and the index node revision field 364 is optional.

The sibling node information 358 includes a sibling node source namefield 368, a sibling minimum index key field 370, and a sibling key typetraits field 372. Inclusion and/or use of the sibling key type traitsfield 372 is optional. The children node information 360 includes one ormore child node information sections 374, 376, etc. corresponding toeach child node of the index node. Each child node information sectionof the one or more child node information sections includes acorresponding child node source name field 378, a corresponding childminimum index key field 380, and a corresponding child key type traitsfield 382. For example, the corresponding child node source name field378 of a child 1 node information section 374 includes a child 1 nodesource name entry. Inclusion and/or use of the corresponding child keytype traits field 382 is optional.

The index node source name field 362 may include an index node dispersedstorage network (DSN) address 354 entry (e.g., source name)corresponding to a storage location for the index node. The index noderevision field 364 may include an index node revision entrycorresponding to a revision number of information contained in the indexnode. Use of the index node revision field 364 enables generating two ormore similar indexes while saving each revision of the two or moresimilar indexes. The node type field 366 includes a node type entry,where the node type entry indicates whether the node is a leaf node ornot a leaf node. The node type indicates that the node is not a leafnode when the node is the index node.

The sibling node source name field 368 includes a sibling node sourcename entry (e.g., sibling node DSN address) corresponding to where asibling node is stored in a DSN memory and/or a distributed storage andtask network (DSTN) module when the index node has the sibling node as asibling. The sibling node is another index node when the index node hasthe sibling. The sibling node source name field 368 may include a nullentry when the index node does not have a sibling. The sibling minimumindex key field 370 includes a sibling of minimum index keycorresponding to the sibling node when the index node has the siblingnode as the sibling. The sibling key type traits field 372 may includesibling key type traits corresponding to the sibling node when the indexnode has the sibling node as the sibling and when the sibling key typetraits field is utilized. Alternatively, index structure metadata mayinclude key type traits utilized globally for each node of the indexstructure.

The index structure metadata may include one or more of key type traitsto be utilized for all nodes of a corresponding index, key type traitsto be utilized for all index nodes of the corresponding index, key typetraits to be utilized for all leaf nodes of the corresponding index, asource name of a root node of the index structure, a maximum number ofindex structure levels, a minimum number of the next level structures, amaximum number of elements per index structure level, a minimum numberof elements per index structure level, and index revision number, and anindex name. The index structure metadata may be utilized for one or moreof accessing the index, generating the index, updating the index, savingthe index, deleting portions of the index, adding a portion to theindex, cloning a portion of the index, and searching through the index.The index structure metadata may be stored in one or more of a localmemory, one or more nodes of the index structure, and as encodedmetadata slices in at least one of the DSTN module and the DSN memory.

The child node source name field 378 includes a child node source nameentry (e.g., child node DSN address) corresponding to a storage locationfor the child node. For example, a child 1 node source name field 378 ofa child 1 node information section 374 includes a child 1 node sourcename. The child minimum index key field 380 includes a child minimumindex key corresponding to the child node. For example, a child 1minimum index key field 380 of the child 1 node information section 374includes a child 1 minimum index key. The child key type traits field382 may include child key type traits corresponding to the child nodewhen the index node has the child node as the child and when the childkey type traits field is utilized. Alternatively, the index structuremetadata may include key type traits utilized globally for each node ofthe index structure.

FIG. 11 is a diagram illustrating an example of a leaf node structure384 that includes leaf node information 388, sibling node information358, and data information 392. Alternatively, there is no sibling nodeinformation 358 when the leaf node has no sibling node. The leaf nodeinformation 388 includes one or more of a leaf node source name field394, a leaf node revision field 396, and a node type field 366.Inclusion and/or use of the leaf node source name field 394 and the leafnode revision field 396 is optional. The sibling node information 358includes a sibling node source name field 368, a sibling minimum indexkey field 370, and a sibling key type traits field 372. Inclusion and/oruse of the sibling key type traits field 372 is optional. The datainformation 392 includes one or more data information sections 398, 400,etc. corresponding to each data object associated with the leaf node.Alternatively, the data information 392 includes null information whenno data object is presently associated with the leaf node. Each datainformation section of the one or more data information sectionsincludes a corresponding data (e.g., data object) source name or datafield 402, a corresponding data index key field 404, and a correspondingdata key type traits field 406. For example, the corresponding datasource name field 402 of a data 1 node information section 398 includesa data 1 source name entry. Inclusion and/or use of the correspondingdata key type traits field 406 is optional.

The leaf node source name field 394 may include a leaf node source nameentry (e.g., leaf node distributed storage and task network (DSTN)address and/or a dispersed storage network (DSN) address) correspondingto a storage location of the leaf node. The leaf node revision field 396may include a leaf node revision entry corresponding to a revisionnumber of information contained in the leaf node. Use of the leaf noderevision enables generating two or more similar indexes while savingeach revision of the two or more similar indexes. The node type field366 includes a node type, where the node type indicates whether the nodeis a leaf node or not a leaf node. The node type indicates that the nodeis a leaf node when the node is the leaf node.

The sibling node source name field 368 includes a sibling node sourcename entry (e.g., sibling node DSN address) corresponding to a storagelocation for a sibling when the leaf node has the sibling node as asibling. The sibling node is another leaf node when the leaf node hasthe sibling. The sibling node source name field 368 may include a nullentry when the leaf node does not have a sibling. The sibling minimumindex key field 370 includes a minimum index key associated with thesibling node when the leaf node has the sibling node as the sibling. Thesibling key type traits field 372 may include sibling key type traitscorresponding to the sibling node when the leaf node has the siblingnode as the sibling and when the sibling key type traits field 372 isutilized. Alternatively, index structure metadata may include key typetraits utilized globally for each leaf node of the index structure.

The data source name or data field 402 includes at least one of a datasource name entry (e.g., a DSN address) corresponding to a storagelocation of data and the data (e.g., a data object, one or more encodeddata slices of data). For example, a data 1 source name or data field402 of a data 1 information section 398 includes a DSN address sourcename of a first data object. As another example, the data 1 source nameor data field 402 of the data 1 information section includes the data 1data object. The data index key field 404 includes a data index keycorresponding to the data. For example, a data 1 index key field orderfor of the data 1 information section 398 includes a data 1 index key.The data key type traits field 406 may include data key type traitscorresponding to the data when the data key type traits field 406 isutilized. Alternatively, the index structure metadata may include keytype traits utilized globally for each data object associated with theindex structure.

FIG. 12 is a schematic block diagram of an embodiment of establishing afallback delegate for updating a hierarchical index structure of a DSN.As shown, the DSN includes a plurality of computing devices 12-16, thenetwork 24, a plurality of delegate devices (e.g., index update modules1-N), and a storage set 85. Each computing device includes adecentralized agreement module 75 and the DST client module 34. Thedecentralized agreement module 75 may be implemented as discussed inco-pending US Patent Application having a title of ACCESSING A DISPERSEDSTORAGE NETWORK, a filing date of May 8, 2015, and a Ser. No.14/707,943. The storage set includes a set of DST execution (EX) units1-n. Note that, each DST execution unit may be interchangeably referredto as a storage unit and the storage set may be interchangeably referredto as a set of storage units.

In an example of operation of the updating of the next node, the DSTclient module 34 of a computing device detects unavailability of anindex update module associated with an update index node request 1,where the DST processing unit 1 updates an index node recovered fromindex slice access messages 1-n from the storage set, generates theupdate index node request 1 based on the updated index node, selects theindex update module 1 (e.g., based on a predetermination, using adeterministic function, etc.), and sends the updated index node requestto the index update module 1. The detecting includes one or more ofinterpreting an unfavorable request response to the update index noderequest, detecting expiration of a request/response timeframe,interpreting an error message, and utilizing a predetermination.

Having detected the unavailability of the index update module 1, the DSTclient module 34 selects another update index module utilizing adeterministic function. The selecting may be based on one or more of anidentifier of the index update module, identifiers of the plurality ofindex update modules, and weights of the plurality of index modules. Forexample, the DST client module 34 utilizes the decentralized agreementmodule to perform a distributed agreement protocol function on theidentifier of the index update module utilizing the weights of theplurality of index modules to produce ranked scoring information,identifies a next ranked scoring, and identifies and index update moduleassociated with the identified the next rank score as the other indexnode. For instance, the DST client module 34 identifies the index updatemodule 2 has been associated with a next highest rank score.

Having selected the other update index module, the DST processing unit 1sends the update index node request to the selected other index updatemodule. For example, the DST client module 34 1 issues, via the network24, an update index node request 2 to the index update module 2. Theother index update module recovers the index node from the storage set,updates the recovered index node based on the update index node request2 to produce an updated index node, and facilitate storage of theupdated index node in the storage set.

FIG. 13 is a logic diagram of an example of a method of establishing afallback delegate for a hierarchical index structure of a DSN. Themethod includes step 100 where a computing device detects unavailabilityof an index node update module associated with an update index noderequest. The detecting includes one or more of interpreting anunfavorable response to a request to the index node update module,detecting expiration of a request/response timeframe, interpreting anerror message, and obtaining a predetermination.

The method continues at step 102 where the computing device selectsanother update index module utilizing a deterministic function. Forexample, the computing device selects him the other update index modulebased on one or more of an identifier of the index update module,identifiers of a plurality of index update modules, and a plurality ofweights associated with the plurality of update index modules. Forinstance, the computing device performs a decentralized agreementprotocol function on the identifier of the update index node requestutilizing the plurality of identifiers of the plurality of index updatemodules, and the plurality of weights of the plurality of index updatemodules to produce ranked scoring information, identifies a next rankedscore, and identifies an index update module associated with theidentified next ranked score as the other index update module.

The method continues at step 104 where the computing device sends theupdate index node request to the other index update module. The methodcontinues at step 106 where the other index update module recovers acopy of the index node from a storage set. For example, the other indexupdate module issues index slice requests, receives index sliceresponses, dispersed storage error decodes received index slices toproduce the copy of the index node.

The method continues at step 108 where the other index update moduleupdates the copy of the index node to produce an updated index nodebased on the update index node request. For example, the other indexupdate module modifies one or more entries of the recovered index nodeutilizing entries extracted from the received update index node requestto produce the updated index node.

The method continues at step 110 where the other index update modulefacilitates storage of the updated index node in the storage set. Forexample, the other index update module dispersed storage error encodesthe updated index node to produce an updated set of index slices, andsends the updated set of index slices to the storage set for storage.

FIG. 14 is a logic diagram of another example of a method ofestablishing a fallback delegate for a hierarchical index structure of aDSN. The method includes step 120 where a device (e.g., a computingdevice, a managing unit, a storage unit, an integrity unit) determinesthat a primary delegate device is unavailable. Note that the primarydelegate device is responsible for changing (e.g., updating, adding,deleting, etc.) one or more nodes of a plurality of nodes of ahierarchical index structure (e.g., FIG. 9).

The method continues at step 122 where the device identifies a fallbackdelegate device for changing the one or more nodes using a deterministicfunction. The deterministic function may implement in a variety of ways.For example, the device performs a first modification of the globalnamespace address of the unavailable primary delegate device to producea first modified address identifier. Note that each delegate device isassigned an individual global namespace address that is partially basedon location within the DSN. As an example, a global namespace address ofa delegate devices includes an MSB section and an LSB section: the MSBsection corresponds to a geographic region of the DSN and the LSBsection corresponds to a unique identifier of a particular delegatedevice within the geographic region.

As another example of the deterministic function, the most significantbits (MSB) of the global namespace address of the unavailable primarydelegate device are modified (e.g., inverted, XORed with a known binarynumber, etc.) to produce a modified MSB. The example continues bydetermining whether the MSB of the global namespace address of the otherdelegate device substantially matches the modified MSB. As a specificexample, the modified MSB is used as an input to a deterministicfunction as described in co-pending patent application mentioned above.When the MSB of the global namespace address of the other delegatedevice substantially matches the modified MSB, the example continues byidentifying the other delegate device as the fallback delegate devicefor the one or more nodes.

The method continues at step 124 where the device determines whetheranother delegate device has a global namespace address corresponding tothe first modified address identifier. For example, the deviceidentifies the other delegate device when the global namespace addressof the other delegate device substantially matches the first modifiedaddress identifier (e.g., selected by the deterministic function module)and determines that the other delegate device is available to become theprimary delegate device. As another example, the device identifies theother delegate device when the global namespace address of the otherdelegate device is a best-available match (e.g., highest ranking fromthe deterministic function module) to the first modified addressidentifier and determines that the other delegate device is available tobecome the primary delegate device.

In some instances, the device will identify two or more potentialfallback delegate devices. In this instance, the device further modifiesthe global namespace address of the unavailable primary delegate deviceto produce a further modified address identifier. The device selects oneof the two or more potential fallback delegate devices as the fallbackdelegate device based on the further modified address identifier.

When the global namespace address of other delegate device correspondsto the first modified address identifier, the method continues at step126 where the device processing a change to a node of the one or morenodes via the other delegate device as the fallback delegate device. Forexample, the device sends a request to the other delegate deviceregarding the change to the node. The example continues with the otherdelegate device determining that it is responsible for executing therequest. When the other delegate device is responsible for executing therequest, the example continues with the other delegate device sending aresponse message to the device indicating that it is responsible forexecuting the request. The example continues with the other delegatedevice executing the change to the node of the one or more nodes.

When the global namespace address of other delegate device does notcorrespond to the first modified address identifier, the methodcontinues at step 128 where the device performs another modification ofthe global namespace address of the unavailable primary delegate device(e.g., include more bits on the MSB section, use less bits on the MSBsection, use a different function than inversion, etc.). An example willbe discussed in greater detail with reference to FIG. 16.

The method continues at step 130 where the device determines whether adelegate device has a global namespace address that corresponds to thefurther modified address identifier of the unavailable delegate device.If yes, the method continues at step 126.

If, after another modification, a delegate device does not have a globalnamespace address that corresponds to the further modified addressidentifier, the method continues at step 132 where the device determineswhether modification options have been exhausted. If not, the methodrepeats at step 128 for another modification. If yes, the methodcontinues at step 134 where the device processes the change to the node.

FIG. 15 is a schematic block diagram of an example of a global namespaceand geographic location with a DSN. In this example, the DSN is dividedinto eight regions; each region is given a digital value ranging from000 to 111. The shape and number of regions may vary greater from theeight with a sector shape. With the DSN, one or more delegate devicesare physically located with each of the regions. The digital value ofthe region constitutes the MSBs of the global namespace address of thedelegates. As such, each delegate device physically located in region000, will have 000 as MSBs of their respective global namespace address.The remainder of the global namespace address is a unique identifier ofa particular delegate device.

For example, if region 000 includes four delegate devices, one will havea global namespace address of 000 00, a second one will have 000 01, athird will have 000 10, and a fourth will have 000 11. Note that theglobal namespace address may be used to identify delegate devices, whichmay have another DSN address to identify them as a computing device, astorage unit, etc. Further note that the global namespace address may bethe sole identifier of the delegate device and its other attributes(e.g., computing device, storage unit, etc.) in the DSN.

FIG. 16 is a diagram of an example of establishing a fallback delegatefor a hierarchical index structure of a DSN. Using the example of FIG.15, which includes eight regions, a first modification of the MSB wouldbe to invert the bits. Thus, 000 and 111 are inversions (or opposites)of each other; 001 and 110 are opposites, 010 and 101 are opposites, and011 and 100 are opposites. As a specific example, if the MSB of theunavailable delegate device is 000, then the first modified address is111. Accordingly, the search for the fallback delegate device would beone that has its MSB as 111. If there is one and it is available, thenit becomes the fallback delegate device. If there are two or more, oneof them is deterministically selected so all devices in the DSN knowwhich one is the fallback delegate device.

If there is not a delegate device with its MSB of 111 that is available,then another modification is made. In this example, a function isperformed to find an MSB value that is in the middle of 000 and 111,which is 010 or 101. Either could be selected. If a fallback delegatedevice is found with its MSB being 010 or 101, then the process ends.If, however, a fallback delegate device is not found, then anothermodification is performed. For example, find the middle between thefirst and second modified addresses and the originals. As a specificexample, the new modification yields an MSB of 011 or 100. If a fallbackdelegate device is found with its MSB begin 011 or 100, then the processends. If, after exhausting the possible modifications (e.g., checkingevery MSB for a fallback delegate device), then the device does not usea delegate device to modify a node of the index structure, it does themodification itself.

It is noted that terminologies as may be used herein such as bit stream,stream, signal sequence, etc. (or their equivalents) have been usedinterchangeably to describe digital information whose contentcorresponds to any of a number of desired types (e.g., data, video,speech, audio, etc. any of which may generally be referred to as‘data’).

As may be used herein, the terms “substantially” and “approximately”provides an industry-accepted tolerance for its corresponding termand/or relativity between items. Such an industry-accepted toleranceranges from less than one percent to fifty percent and corresponds to,but is not limited to, component values, integrated circuit processvariations, temperature variations, rise and fall times, and/or thermalnoise. Such relativity between items ranges from a difference of a fewpercent to magnitude differences. As may also be used herein, theterm(s) “configured to”, “operably coupled to”, “coupled to”, and/or“coupling” includes direct coupling between items and/or indirectcoupling between items via an intervening item (e.g., an item includes,but is not limited to, a component, an element, a circuit, and/or amodule) where, for an example of indirect coupling, the intervening itemdoes not modify the information of a signal but may adjust its currentlevel, voltage level, and/or power level. As may further be used herein,inferred coupling (i.e., where one element is coupled to another elementby inference) includes direct and indirect coupling between two items inthe same manner as “coupled to”. As may even further be used herein, theterm “configured to”, “operable to”, “coupled to”, or “operably coupledto” indicates that an item includes one or more of power connections,input(s), output(s), etc., to perform, when activated, one or more itscorresponding functions and may further include inferred coupling to oneor more other items. As may still further be used herein, the term“associated with”, includes direct and/or indirect coupling of separateitems and/or one item being embedded within another item.

As may be used herein, the term “compares favorably”, indicates that acomparison between two or more items, signals, etc., provides a desiredrelationship. For example, when the desired relationship is that signal1 has a greater magnitude than signal 2, a favorable comparison may beachieved when the magnitude of signal 1 is greater than that of signal 2or when the magnitude of signal 2 is less than that of signal 1. As maybe used herein, the term “compares unfavorably”, indicates that acomparison between two or more items, signals, etc., fails to providethe desired relationship.

As may also be used herein, the terms “processing module”, “processingcircuit”, “processor”, and/or “processing unit” may be a singleprocessing device or a plurality of processing devices. Such aprocessing device may be a microprocessor, micro-controller, digitalsignal processor, microcomputer, central processing unit, fieldprogrammable gate array, programmable logic device, state machine, logiccircuitry, analog circuitry, digital circuitry, and/or any device thatmanipulates signals (analog and/or digital) based on hard coding of thecircuitry and/or operational instructions. The processing module,module, processing circuit, and/or processing unit may be, or furtherinclude, memory and/or an integrated memory element, which may be asingle memory device, a plurality of memory devices, and/or embeddedcircuitry of another processing module, module, processing circuit,and/or processing unit. Such a memory device may be a read-only memory,random access memory, volatile memory, non-volatile memory, staticmemory, dynamic memory, flash memory, cache memory, and/or any devicethat stores digital information. Note that if the processing module,module, processing circuit, and/or processing unit includes more thanone processing device, the processing devices may be centrally located(e.g., directly coupled together via a wired and/or wireless busstructure) or may be distributedly located (e.g., cloud computing viaindirect coupling via a local area network and/or a wide area network).Further note that if the processing module, module, processing circuit,and/or processing unit implements one or more of its functions via astate machine, analog circuitry, digital circuitry, and/or logiccircuitry, the memory and/or memory element storing the correspondingoperational instructions may be embedded within, or external to, thecircuitry comprising the state machine, analog circuitry, digitalcircuitry, and/or logic circuitry. Still further note that, the memoryelement may store, and the processing module, module, processingcircuit, and/or processing unit executes, hard coded and/or operationalinstructions corresponding to at least some of the steps and/orfunctions illustrated in one or more of the Figures. Such a memorydevice or memory element can be included in an article of manufacture.

One or more embodiments have been described above with the aid of methodsteps illustrating the performance of specified functions andrelationships thereof. The boundaries and sequence of these functionalbuilding blocks and method steps have been arbitrarily defined hereinfor convenience of description. Alternate boundaries and sequences canbe defined so long as the specified functions and relationships areappropriately performed. Any such alternate boundaries or sequences arethus within the scope and spirit of the claims. Further, the boundariesof these functional building blocks have been arbitrarily defined forconvenience of description. Alternate boundaries could be defined aslong as the certain significant functions are appropriately performed.Similarly, flow diagram blocks may also have been arbitrarily definedherein to illustrate certain significant functionality.

To the extent used, the flow diagram block boundaries and sequence couldhave been defined otherwise and still perform the certain significantfunctionality. Such alternate definitions of both functional buildingblocks and flow diagram blocks and sequences are thus within the scopeand spirit of the claims. One of average skill in the art will alsorecognize that the functional building blocks, and other illustrativeblocks, modules and components herein, can be implemented as illustratedor by discrete components, application specific integrated circuits,processors executing appropriate software and the like or anycombination thereof.

In addition, a flow diagram may include a “start” and/or “continue”indication. The “start” and “continue” indications reflect that thesteps presented can optionally be incorporated in or otherwise used inconjunction with other routines. In this context, “start” indicates thebeginning of the first step presented and may be preceded by otheractivities not specifically shown. Further, the “continue” indicationreflects that the steps presented may be performed multiple times and/ormay be succeeded by other activities not specifically shown. Further,while a flow diagram indicates a particular ordering of steps, otherorderings are likewise possible provided that the principles ofcausality are maintained.

The one or more embodiments are used herein to illustrate one or moreaspects, one or more features, one or more concepts, and/or one or moreexamples. A physical embodiment of an apparatus, an article ofmanufacture, a machine, and/or of a process may include one or more ofthe aspects, features, concepts, examples, etc. described with referenceto one or more of the embodiments discussed herein. Further, from figureto figure, the embodiments may incorporate the same or similarly namedfunctions, steps, modules, etc. that may use the same or differentreference numbers and, as such, the functions, steps, modules, etc. maybe the same or similar functions, steps, modules, etc. or differentones.

Unless specifically stated to the contra, signals to, from, and/orbetween elements in a figure of any of the figures presented herein maybe analog or digital, continuous time or discrete time, and single-endedor differential. For instance, if a signal path is shown as asingle-ended path, it also represents a differential signal path.Similarly, if a signal path is shown as a differential path, it alsorepresents a single-ended signal path. While one or more particulararchitectures are described herein, other architectures can likewise beimplemented that use one or more data buses not expressly shown, directconnectivity between elements, and/or indirect coupling between otherelements as recognized by one of average skill in the art.

The term “module” is used in the description of one or more of theembodiments. A module implements one or more functions via a device suchas a processor or other processing device or other hardware that mayinclude or operate in association with a memory that stores operationalinstructions. A module may operate independently and/or in conjunctionwith software and/or firmware. As also used herein, a module may containone or more sub-modules, each of which may be one or more modules.

As may further be used herein, a computer readable memory includes oneor more memory elements. A memory element may be a separate memorydevice, multiple memory devices, or a set of memory locations within amemory device. Such a memory device may be a read-only memory, randomaccess memory, volatile memory, non-volatile memory, static memory,dynamic memory, flash memory, cache memory, and/or any device thatstores digital information. The memory device may be in a form a solidstate memory, a hard drive memory, cloud memory, thumb drive, servermemory, computing device memory, and/or other physical medium forstoring digital information.

While particular combinations of various functions and features of theone or more embodiments have been expressly described herein, othercombinations of these features and functions are likewise possible. Thepresent disclosure is not limited by the particular examples disclosedherein and expressly incorporates these other combinations.

What is claimed is:
 1. A method for execution by a device of a dispersedstorage network (DSN), the method comprises: determining that a primarydelegate device is unavailable, wherein the primary delegate device isresponsible for changing one or more nodes of a plurality of nodes of ahierarchical index structure, wherein the hierarchical index structureis used to identify particular data stored in the DSN and wherein theplurality of nodes includes a root index node, a plurality of indexnodes, and a plurality of leaf index nodes arranged in a relatedhierarchical manner; and identifying a fallback delegate device forchanging the one or more nodes using a deterministic function thatincludes: performing a first modification of global namespace address ofthe unavailable primary delegate device to produce a first modifiedaddress identifier, wherein each delegate device of a plurality ofdelegate devices is assigned an individual global namespace address thatis partially based on location within the DSN; determining whetheranother delegate device of the plurality of delegate devices has aglobal namespace address corresponding to the first modified addressidentifier; and when the global namespace address of other delegatedevice corresponds to the first modified address identifier, processinga change to a node of the one or more nodes via the other delegatedevice as the fallback delegate device.
 2. The method of claim 1 furthercomprises: modifying most significant bits (MSB) of the global namespaceaddress of the unavailable primary delegate device to produce a modifiedMSB; and determining whether the MSB of the global namespace address ofthe other delegate device substantially matches the modified MSB; andwhen the MSB of the global namespace address of the other delegatedevice substantially matches the modified MSB, identifying the otherdelegate device as the fallback delegate device for the one or morenodes.
 3. The method of claim 2, wherein the individual global namespaceaddress comprises: the MSB corresponding to a geographic region of theDSN that is partially based on location within the DSN; and lesssignificant bits (LSB) corresponding to a unique identifier of aparticular delegate device within the geographic region.
 4. The methodof claim 1, determining whether another delegate device of the pluralityof delegate devices has a global namespace address corresponding to thefirst modified address identifier comprises at least one of: determiningthat the global namespace address of the other delegate devicesubstantially matches the first modified address identifier anddetermining that the other delegate device is available to become theprimary delegate device; and determining that the global namespaceaddress of the other delegate device is a best-available match to thefirst modified address identifier and determining that the otherdelegate device is available to become the primary delegate device. 5.The method of claim 1, wherein the determining whether another delegatedevice of the plurality of delegate devices has a global namespaceaddress corresponding to the first modified address identifiercomprises: identifying two other delegate devices as potential fallbackdelegate devices using a first pass of a modified address of theunavailable primary delegate device; and changing the first passmodified address to the first modified address identifier to select theother delegate device from the two delegate devices.
 6. The method ofclaim 1 further comprises: inverting most significant bits (MSB) of theglobal namespace address of the unavailable primary delegate device toproduce the first modified address identifier; when the global namespaceaddress of the other delegate device does not correspond to the firstmodified address identifier: performing a second modification to thefirst modified address identifier to produce a second modified addressidentifier; and determining that a second other delegate device of theplurality of delegate devices has a global namespace addresscorresponding to the second modified address identifier; and processinga change to a node of the one or more nodes via the second otherdelegate device as the fallback delegate device.
 7. The method of claim6 further comprises: when the global namespace address of the secondother delegate device does not correspond to the second modified addressidentifier: continuing to perform modifications of a current modifiedaddress identifier until one of the plurality of delegate devices isidentified as the fallback delegate device or until the modificationshave been exhausted; and when the modifications have been exhausted,processing, by the device, the change to a node of the one or morenodes.
 8. The method of claim 1, wherein the processing the change tothe node of the one or more nodes via the other delegate devicecomprises: sending, by the device, a request to the other delegatedevice regarding the change to the node of the one or more nodes;determining, by the other delegate device, whether the other delegatedevice is responsible for executing the change type specific request;and when the other delegate device is responsible for executing therequest: sending, by the other delegate device, a response message tothe device indicating that the other delegate device is responsible forexecuting the request; and executing, by the other delegate device, thechange to the node of the one or more nodes.
 9. The method of claim 8,wherein the determining whether the other delegate device is responsiblefor executing the change type specific request comprises: performing thefirst modification of the global namespace address of the unavailableprimary delegate device to produce the first modified addressidentifier; and determining that the other delegate device has theglobal namespace address corresponding to the first modified addressidentifier.
 10. A computer readable memory comprises: a first memoryelement that stores operational instructions that, when executed by adevice of a dispersed storage network (DSN), causes the device to:determine that a primary delegate device is unavailable, wherein theprimary delegate device is responsible for changing one or more nodes ofa plurality of nodes of a hierarchical index structure, wherein thehierarchical index structure is used to identify particular data storedin the DSN and wherein the plurality of nodes includes a root indexnode, a plurality of index nodes, and a plurality of leaf index nodesarranged in a related hierarchical manner; and a second memory elementthat stores operational instructions that, when executed by the device,causes the device to: identify a fallback delegate device for changingthe one or more nodes using a deterministic function that includes:perform a first modification of global namespace address of theunavailable primary delegate device to produce a first modified addressidentifier, wherein each delegate device of a plurality of delegatedevices is assigned an individual global namespace address that ispartially based on location within the DSN; determine whether anotherdelegate device of the plurality of delegate devices has a globalnamespace address corresponding to the first modified addressidentifier; and when the global namespace address of other delegatedevice corresponds to the first modified address identifier, process achange to a node of the one or more nodes via the other delegate deviceas the fallback delegate device.
 11. The computer readable memory ofclaim 10, wherein the second memory element further stores operationalinstructions that, when executed by the device, causes the device to:modify most significant bits (MSB) of the global namespace address ofthe unavailable primary delegate device to produce a modified MSB; anddetermine whether the MSB of the global namespace address of the otherdelegate device substantially matches the modified MSB; and when the MSBof the global namespace address of the other delegate devicesubstantially matches the modified MSB, identify the other delegatedevice as the fallback delegate device for the one or more nodes. 12.The computer readable memory of claim 11, wherein the individual globalnamespace address comprises: the MSB corresponding to a geographicregion of the DSN that is partially based on location within the DSN;and less significant bits (LSB) corresponding to a unique identifier ofa particular delegate device within the geographic region.
 13. Thecomputer readable memory of claim 10, wherein the second memory elementfurther stores operational instructions that, when executed by thedevice, causes the device to determine whether another delegate deviceof the plurality of delegate devices has the global namespace addresscorresponding to the first modified address identifier by at least oneof: determining that the global namespace address of the other delegatedevice substantially matches the first modified address identifier anddetermining that the other delegate device is available to become theprimary delegate device; and determining that the global namespaceaddress of the other delegate device is a best-available match to thefirst modified address identifier and determining that the otherdelegate device is available to become the primary delegate device. 14.The computer readable memory of claim 10, wherein the second memoryelement further stores operational instructions that, when executed bythe device, causes the device to determine whether another delegatedevice of the plurality of delegate devices has the global namespaceaddress corresponding to the first modified address identifiercomprises: identifying two other delegate devices as potential fallbackdelegate devices using a first pass of a modified address of theunavailable primary delegate device; and changing the first passmodified address to the first modified address identifier to select theother delegate device from the two delegate devices.
 15. The computerreadable memory of claim 10, wherein the second memory element furtherstores operational instructions that, when executed by the device,causes the device to: invert most significant bits (MSB) of the globalnamespace address of the unavailable primary delegate device to producethe first modified address identifier; when the global namespace addressof the other delegate device does not correspond to the first modifiedaddress identifier: perform a second modification to the first modifiedaddress identifier to produce a second modified address identifier;determine that a second other delegate device of the plurality ofdelegate devices has a global namespace address corresponding to thesecond modified address identifier; and process a change to a node ofthe one or more nodes via the second other delegate device as thefallback delegate device.
 16. The computer readable memory of claim 15,wherein the second memory element further stores operationalinstructions that, when executed by the device, causes the device to:when the global namespace address of the second other delegate devicedoes not correspond to the second modified address identifier: continueto perform modifications of a current modified address identifier untilone of the plurality of delegate devices is identified as the fallbackdelegate device or until the modifications have been exhausted; and whenthe modifications have been exhausted, process, by the device, thechange to a node of the one or more nodes.
 17. The computer readablememory of claim 10 further comprises: the second memory element furtherstores operational instructions that, when executed by the device,causes the device to processing the change to the node of the one ormore nodes via the other delegate device by: send a request to the otherdelegate device regarding the change to the node of the one or morenodes; and a third memory element that stores operational instructionsthat, when executed by the other delegate device, causes the otherdelegate device to: determine whether the other delegate device isresponsible for executing the change type specific request; and when theother delegate device is responsible for executing the request: send aresponse message to the device indicating that the other delegate deviceis responsible for executing the request; and execute the change to thenode of the one or more nodes.
 18. The computer readable memory of claim17, wherein the third memory element further stores operationalinstructions that, when executed by the other delegate device, causesthe other delegate device to determine whether the other delegate deviceis responsible for executing the change type specific request by:performing the first modification of the global namespace address of theunavailable primary delegate device to produce the first modifiedaddress identifier; and determining that the other delegate device hasthe global namespace address corresponding to the first modified addressidentifier.